The present invention relates to substituted quinolone derivatives wherein an oxazolidinone, isoxazolinone, or isoxazoline compound is chemically combined with a quinolone. The present invention also relates to a method of preparing pharmacologically active quinolone derivatives and various intermediates used in the method. The present quinolone derivatives are useful as broad spectrum antimicrobial agents effective against a number of human and veterinary Gram positive and Gram negative pathogens, including the Staphylococci, for example S. aureus; Enterococci, for example E. faecalis; Streptococci, for example S. pneumoniae; Haemophilus, for example H. influenza; Moraxella, for example M. catarrhalis; and Escherichia for example E. coli; Mycobacteria, for example M. tuberculosis; intercellular microbes, for example Chlamydia and Rickettsiae; and Mycoplasma, for example M. pneumoniae, amongst others. The present invention also relates to pharmaceutical compositions containing the quinolone derivatives, to methods of treating a bacterial infection using the quinolone derivatives, and to a process for producing the quinolone derivatives.
The increase in bacterial resistance to existing antibacterial agents is a major clinical problem. Accordingly, there is a need in the art for compounds, compositions, and methods of treating warm-blooded animals that suffer from a bacterial infection and are resistant to conventional antibacterial treatments. The development and increase in resistance to the quinolone carboxylic acid class of antibacterial compounds has not been as pervasive as with other antibacterial agents. Therefore, new quinolone carboxylic acid compounds may be useful in combating resistant bacteria.
The 7-substituted quinolone carboxylic acid derivatives, represented by the general formula (II), wherein Y is either C-R5 or N, and R1 through R5 include a wide variety of substituents, are well known as anti-fungal and anti-bacterial agents, and as synthetic intermediates to related compounds. The 7-substituted derivatives of compound (II) include the antibacterials cinoxacin (U.S. Pat. No. 3,669,965); ciprofloxacin (U.S. Pat. Nos. 4,563,459 and 4,620,007); ofloxacin (U.S. Pat. No. 4,382,892); and levofloxacin (U.S. Pat. Nos. 4,985,557, 5,053,407, and 5,142,046). 
Oxazolidinones having a general structural formula (III) also are a well known class of orally active, synthetic antibacterial agents. The literature contains numerous references to oxazolidinones (III), wherein R1 through R3 include a wide variety of substituents. Oxazolidinones having one or two substituents on the phenyl ring are disclosed in U.S. Pat. Nos. 4,705,799; 5,523,403; and 5,654,435, for example. Oxazolidinones (III) include the antibacterial agent designated as DuP 721, see J. Med. Chem., 32, 1673 (1989). 
Oxazolidinones (III) having an arylbenzene substituent on the oxazolidinone ring are disclosed in U.S. Pat. Nos. 4,948,801 and 5,130,316. 3-[(Di- or fused-ring substituted)phenyl]-2-oxazolidinones are disclosed in U.S. Pat. Nos. 4,977,173; 4,921,869; 4,801,600; and 5,164,510. European Patent Applications 0 697 412; 0 694 544; 0 694 543; and 0 693 491, and International Patent Publication No. WO 93/09103, disclose 5- to 9-membered substituted aryl- and heteroaryl-phenyl oxazolidinones as antibacterial agents. U.S. Pat. No. 5,254,577 discloses aminomethyloxooxazolidinyl arylbenzene derivatives as antibacterial agents. Other references disclosing oxazolidinones include U.S. Pat. Nos. 4,801,600 and 4,921,869. Some of the pyridine-substituted phenyl oxazolidinone derivatives disclosed in the above patents are effective against Gram positive bacteria, such as Staphylococcus aureus and Streptococcus pneumoniae. However, the oxazolidinones are not active against Gram negative bacteria, such as Escherichia coli, Klebsiella, Proteus, and Seratia marcenses. Moreover, oxazolidinones cannot be administered as an injection solution because their free amino forms are sparingly soluble.
Isoxazolinone derivatives having a general structural formula (IV) are disclosed in WO 00/10566 as anti-bacterial agents. Simple isoxazolinones also are used as preemergent herbicides. For example, U.S. Pat. No. 4,065,463 discloses 2-methyl-4-(chloro-m-tolyl)-3-isoxazolin-5-one, which is useful in preventing weed growth. 
Isoxazoline derivatives having a general structural formula (V) are disclosed in WO 99/41244, WO 98/07708 and U.S. Pat. No. 3,769,295 as anti-microbial agents. Simple isoxazolines also are used as preemergent herbicides. In addition, U.S. Pat. No. 4,283,403 discloses 3-aryl-2-isoxazolines, which are useful in preventing plant fungal diseases. 
Although quinolones, oxazolidinones, isoxazolinones, and isoxazolines are known, applicants are aware of no reference which discloses covalently bonding a quinolone to an oxazolidinone, an isoxazolinone, or an isoxazoline, and using the resulting quinolone derivatives as broad spectrum anti-bacterial agents against both Gram positive and Gram negative bacteria.
The present invention is directed to structurally novel compounds produced by covalently bonding an antibacterial oxazolidinone, isoxazolinone, or isoxazoline compound to a substituted quinolone compound. The compounds of the present invention have a quinolone structure substituted with an oxazolidinone, isoxazolinone, or isoxazoline via a linking group at the 1- or 7-position of the quinolone.
The present compounds are active against Gram negative bacteria and Gram positive bacteria, and accordingly are useful as broad spectrum antibacterial agents. The present compounds are surprisingly effective against a number of human and veterinary pathogens, including Staphylococci, for example S. aureus; Enterococci, for example E. faecalis; Streptococci, for example S. pneumoniae; Haemophilus, for example H. influenza; Moraxella, for example M. catarrhalis; and Escherichia for example E. coli. Other examples include Mycobacteria, for example M. tuberculosis; intercellular microbes, for example Chlamydia and Rickettsiae; and Mycoplasma, for example M. pneumoniae. The present compounds also are envisioned as cytotoxic anticancer agents.
Syntheses of simple quinolone derivatives are well known in the art. However, the synthesis of a quinolone covalently linked to an oxazolidinone, an isoxazolinone, or an isoxazoline is not straightforward. Thus, a method of synthesizing compounds of the present invention also is disclosed.
One aspect of the present invention is to provide substituted quinolone derivatives having a structural formula (I): 
or a pharmaceutically acceptable salt, hydrate, or prodrug thereof,
wherein Y1 is CH or N;
Y2, Y3, and Y4, independently, are C or N;
L is a bond or is a linker group attached to a carbon at the seven quinolone ring position or to an N at the one quinolone ring position, and selected from the group consisting of a bond, NR7, and NR8(CR92)nNR8;
m is 0 or 1,
n is 0-3;
Q is selected from the group consisting of 
R1 is selected from the group consisting of null, H, C1-C4alkyl, C3-C5cycloalkyl, C1-C4haloalkyl, and halophenyl;
R2 is null when Y2 is N, or is selected from the group consisting of H, alkyl, C1-C2alkoxy, halo, and haloalkoxy, when Y2 is C, or when Y2 is C, R1 and R2 can be taken together to form a 5- or 6-membered, optionally substituted, heteroalkyl or heteroaryl ring;
R3 is H or F when Y3 is C, or R3 is null when Y3 is N;
R4 is selected from the group consisting of H, methyl, amino, and F; R5 is selected from the group consisting of H, methyl, hydroxy, and halo;
R6 is selected from the group consisting of H, methyl, hydroxy, and halo, when Y4 is C, or R6 is null when Y4 is N;
R7 is selected from the group consisting of H, C1-C4 alkyl, formyl, alkylcarbonyl, alkylsulfonyl, and alkoxycarbonyl;
R8, independently, are H or C1-C4alkyl, or are taken together to form a 4- to 9-membered, optionally substituted, heteroalkyl or heteroaryl ring;
R9, independently, are H or C1-C4alkyl, or are taken together to form a 4- to 9-membered heterocyclic or heterobicyclic ring, optionally substituted with C1-C2alkyl, haloalkyl, or methoximino;
R10 is selected from the group consisting of OH, alkoxy, aryloxy, and NHC(xe2x95x90Z)R11;
R11 is selected from the group consisting of H, C1-C7alkyl, C3-C5cycloalkyl, hydroxymethyl, haloalkyl, CH2SMe, NR122, C1-C4alkoxy, and aryloxy;
R12 is C1-C4alkyl; and
Z is O or S.
Another aspect of the present invention is to provide a pharmaceutical composition containing a compound of formula (I) and a pharmaceutical acceptable carrier, diluent, or excipient.
One other aspect of the present invention is to provide a method of treating microbial infections in a mammal comprising administering to the mammal a pharmaceutically effective amount of a compound of formula (I).
Another aspect of the present invention is to provide method of treating a cancer comprising administering to a mammal in need thereof a pharmaceutically effective amount of a compound of formula (I).
Yet another aspect of the present invention is to provide a method of manufacturing a compound of structural formula (I).
As used herein, the terms and phrases have the meanings and definitions known in the art. Some of the more commonly used phrases are described in more detail below.
xe2x80x9cAlkylxe2x80x9d refers to a cyclic, branched, or straight chain chemical group containing only carbon and hydrogen atoms, for example methyl, pentyl, and adamantyl. Alkyl groups can be unsubstituted or substituted with one or more substituents, e.g., halogen, alkoxy, acyloxy, amino, hydroxyl, mercapto, carboxy, benzyloxy, phenyl, and benzyl. Alkyl groups can be saturated or unsaturated (e.g., containing alkenyl or alkynyl subunits), at one or several positions. Typically, alkyl groups contain 1 to about 12 carbon atoms, for example 1 to about 10, or 1 to about 8 carbon atoms.
xe2x80x9cHeteroalkylxe2x80x9d refers to a cyclic, branched, or straight chain chemical group containing carbon, hydrogen and at least one heteroatom. Heteroalkyl includes bicyclic compounds. The heteroatom typically is nitrogen, oxygen, or sulfur. Heteroalkyl groups can be unsubstituted or substituted with one or more substituents, e.g., halogen, alkoxy, acyloxy, amino, hydroxyl, mercapto, carboxy, benzyloxy, phenyl, and benzyl. When the heteroalkyl group contains a nitrogen atom, the nitrogen atom can be primary, secondary, tertiary, or quaternary, or can be in various forms such as an amide or sulfonamide. Heteroalkyl groups can contain one or more unsaturated (e.g., alkenyl or alkynyl) subunits. Typically, heteroalkyl groups contain 1 to about 12 atoms, for example 1 to about 8, or 1 to about 4 carbon atoms.
xe2x80x9cArylxe2x80x9d refers to a monovalent aromatic carbocyclic group having a single ring (e.g. phenyl), multiple rings (e.g. biphenyl), or multiple condensed rings (e.g. naphthyl or anthryl). Aryl groups can be unsubstituted or substituted with amino, hydroxyl, alkyl, heteroalkyl, alkoxy, halo, mercapto, and other substituents. Typically, the aryl group is a substituted single ring compound. For example, the aryl group is a substituted phenyl ring.
xe2x80x9cHeteroarylxe2x80x9d refers to a monovalent aromatic group having a single ring (e.g., pyridyl or furyl) or multiple condensed rings (e.g., indolizinyl or benzothienyl) containing carbon atoms and having at least one heteroatom within the ring. The heteroatom preferably is nitrogen, oxygen or sulfur. Heteroaryl groups can be optionally unsubstituted or substituted with amino, hydroxyl, alkyl, heteroalky, alkoxy, halo, mercapto, and other substituents. In one embodiment, the heteroaryl group is substituted pyridyl.
The term xe2x80x9chaloxe2x80x9d or xe2x80x9chalogenxe2x80x9d is defined herein to include fluorine, bromine, chlorine, and iodine.
The term xe2x80x9chaloalkylxe2x80x9d is defined herein as an alkyl group substituted with one or more halo substituents, either fluoro, chloro, bromo, iodo, or combinations thereof. Similarly, xe2x80x9chalocycloalkylxe2x80x9d is defined as a cycloalkyl group having one or more halo substituents.
The term xe2x80x9calkoxyxe2x80x9d and xe2x80x9caryloxy xe2x80x9d are defined as xe2x80x94OR, wherein R is alkyl or aryl, respectfully.
The term xe2x80x9chydroxyxe2x80x9d is defined as xe2x80x94OH.
The term xe2x80x9caminoxe2x80x9d is defined as xe2x80x94NR2, wherein each R, independently, is alkyl or hydrogen.
The term xe2x80x9calkylcarbonylxe2x80x9d is defined as Rxe2x80x94C(xe2x95x90O)xe2x80x94, where R is alkyl.
The term xe2x80x9calkoxycarbonylxe2x80x9d is defined as ROxe2x80x94C(xe2x95x90O)xe2x80x94, where R is alkyl.
The term xe2x80x9calkylsulfonyl xe2x80x9d is defined as Rxe2x80x94SO3, where R is alkyl.
The quinolone ring system is numbered as follows: 
xe2x80x9cBiologically active compoundsxe2x80x9d or xe2x80x9cbioactive compoundsxe2x80x9d refers to present quinolone derivatives that exhibit biological activity. For instance, a biologically active compound can inhibit the interaction between an enzyme or receptor and its respective substrate(s) or endogenous ligand(s), or inhibit cell growth of a microorganism, by about at least 15% at a solution concentration of 10xe2x88x923 molar or lower (i.e., has inhibitory activity). For example, a biologically active compound can inhibit such processes at solution concentrations of about 10xe2x88x924 M or lower, preferably 10xe2x88x925 M or lower, and more preferably about 10xe2x88x926 M or lower.
The present invention is directed to quinolone-oxazolidinones, quinolone-isoxazolinones, and quilolone-isoxazolines of structural formula (I) as defined below: 
or a pharmaceutically acceptable salt, hydrate, or prodrug thereof,
wherein Y1 is CH or N;
Y2, Y3, and Y4, independently, are C or N;
L is a bond or is a linker group attached to a carbon at the seven quinolone ring position or to an N at the one quinolone ring position, and selected from the group consisting of a bond, NR7, and NR8(CR92)nNR8;
m is 0 or 1;
n is 0-3;
Q is selected from the group consisting of 
R1 is selected from the group consisting of null, H, C1-C4alkyl, C3-C5cycloalkyl, C1-C4haloalkyl, and halophenyl;
R2 is null when Y2 is N, or is selected from the group consisting of H, alkyl, C1-C2alkoxy, halo, and haloalkoxy, when Y2 is C, or when Y2 is C, R1 and R2 can be taken together to form a 5- or 6-membered, optionally substituted, heteroalkyl or heteroaryl ring;
R3 is H or F when Y3 is C, or R3 is null when Y3 is N;
R4 is selected from the group consisting of H, methyl, amino, and F; R5 is selected from the group consisting of H, methyl, hydroxy, and halo;
R6 is selected from the group consisting of H, methyl, hydroxy, and halo, when Y4 is C, or R6 is null when Y4 is N;
R7 is selected from the group consisting of H, C1-C4 alkyl, formyl, alkylcarbonyl, alkylsulfonyl, and alkoxycarbonyl;
R8, independently, are H or C1-C4alkyl, or are taken together to form a 4- to 9-membered, optionally substituted, heteroalkyl or heteroaryl ring;
R9, independently, are H or C1-C4alkyl, or are taken together to form a 4- to 9-membered heterocyclic or heterobicyclic ring, optionally substituted with C1-C2alkyl, haloalkyl, or methoximino;
R10 is selected from the group consisting of OH, alkoxy, aryloxy, and NHC(xe2x95x90Z)R11;
R11 is selected from the group consisting of H, C1-C7alkyl, C3-C5cycloalkyl, hydroxymethyl, haloalkyl, CH2SMe, NR12 2, C1-C4alkoxy, and aryloxy;
R12 is C1-C4alkyl; and
Z is O or S.
The compounds of the present invention are effective antimicrobial agents against a number of human and veterinary pathogens, including Gram-positive, Gram negative, and anaerobic bacteria, and in treating microbial infections in mammals. The present compounds also can be used as cytotoxic anticancer compounds.
Preferred compounds of general formula (I), are those wherein:
Y1 is CH;
Y2, Y3, and Y4 are C;
L is a bond or NR8(CR92)nNR8;
n is 2,
R3 is H or F;
R4 is H, methyl, amino, or F;
R5 and R6, independently, are H, methyl, hydroxy, or halo;
R10 is OH, alkoxy, aryloxy, or NHC(Z)R11 when Q is an oxazolidinone or isoxazoline group, or is aryloxy, NHC(Z)R11, when Q is a isoxazoline group; and Z is O.
A preferred Q is an oxazolidinone group. Preferred Lxe2x80x94Q groups, wherein m is zero, are selected from the group consisting of: 
wherein R13 and R14, independently, are H, C1-2alkyl, or C1-2 haloalkyl, or are taken together to form a cyclopropyl or methoximino group.
It also is preferred that compounds of formula (I) are optically pure enantiomers having the S-configuration at the five-position carbon of the oxazolidinone or isoxazoline ring.
Preferred compounds of the present invention include (Ac is C(xe2x95x90O)CH3): 
The present invention is also directed to methods of synthesizing pharmaceutically active oxazolidinone-, isoxazoline-, and isoxazolinone-substituted quinolones (I) and intermediate compounds used in the synthesis. The substituted quinolone derivatives of the present invention can be prepared by the following general synthetic schemes.
Scheme 1 illustrates one general method of synthesizing the 7-oxazolidinone-, isoxazoline-, and isoxazolinone-substituted quinolone compounds (B) of the present invention. Scheme 2 illustrates specific examples of synthesizing oxazolidinone-substituted quinolone compounds (3 and 6) of the present invention. 
In Scheme 1, an appropriately substituted quinolone, preferably containing a leaving group (LG) at the 7-position (compound A), such as a fluoro, chloro, or triflate derivative, is used as a starting material. Specific examples of such compounds are illustrated by compounds (1), (4), and (5). Compounds (1), (4), and (5) are readily available from a number of commercial sources or, alternatively, are known in the chemical literature or can be readily prepared by one skilled in the art. 7-Chloro-1-cyclopropyl-6-fluoro-4-oxohydroquinoline-3-carboxylic acid (1) is commercially available from Acros Organics, and its synthesis is described in German Patents DE 3142854, DE 3248505, and DE 3248507. 1-Cyclopropyl-6,7-difluoro-4-oxo-3-quinolinecarboxylic acid is commercially available from Louston International, and its synthesis is described in German patent DE3248507. 9,10-Difluoro-3-methyl-7-oxo-2,3-dihydro-7H-[1,4]oxazino[2,3,4-xcex]quinoline-6-carboxylic acid is commercially available from Maybridge Chemical Company and its synthesis is described in Japanese patents JP 57088182 and JP 58072589 and EP 47005. 9-Chloro-10-fluoro-3-methyl-7-oxo-2,3-dihydro-7H-[1,4]oxazino[2,3,4-xcex]quinoline-6-carboxylic acid is commercially available from Commercially available from Zhejiang Hengdian Imp. and Exp. Co., Ltd. and its synthesis is described in Chem. Pharm. Bull., 32, 4907-13 (1984) and EP 206283.
In one embodiment, the appropriately substituted quinolone (1), (4), or (5) is treated with an oxazolidinone, isoxazoline, or isoxazolinone substituted with an sufficiently nucleophilic linking group, L, such that the subsequent nucleophilic substitution reaction provides, in a one-pot reaction sequence, the respective crude oxazolidinone-, isoxazoline-, or isoxazolinone-substituted quinolone (I).
The L group on the oxazolidinone, isoxazoline, or isoxazolinone can be introduced by standard synthetic methods from commercially available reagents as described hereafter. For example, when quinolone (1), (4), or (5) is treated with 5-(S)-aminomethyl-3-(3-fluoro-4-piperazinophenyl)oxazolidine-2-one in N-methylpyrroline-2-one (NMP) and N-methylmorpholine (NMM), the respective crude oxazolidinone-substituted quinolone (3) or (6) is formed in moderate to high yield. Compounds (3) and (6) then can be purified following chromatographic techniques well known in the art.
Alternately, Scheme 3 outlines a representative procedure for preparing compounds where a carbon-carbon bond connects the quinolone fragment to a phenyloxazolidinone subunit. Quinolone triflates 7a,b, (Kiely et. al. J. 
Heterocyclic Chem. 1991, 28, 1581-1585), is reacted with boronic acid 8 in the presence of 1,2-dimethoxyethane, aqueous dibasic potassium phosphate and a suitable palladium catalyst, such as bis(triphenylphosphine)palladium bichloride or tetrakis(triphenylphosphine)palladium, and at a suitable temperature, preferably at reflux, to generate the respective coupled products 9a,b. It will be apparent to one skilled in the art that compounds 9a,b are both antimicrobial compounds and synthetic intermediates. For example, the tert-butoxycarbonyl (BOC) moiety of 9a,b can be removed with, for example, trifluoroacetic acid to give an amino intermediate which can be further elaborated, for example, acylated, employing conditions described below. Additionally, the ester moiety of 10 or a subsequent acylated derivative can be hydrolyzed under acidic or basic conditions to give the corresponding carboxylic acid 11. Furthermore, when R1=Bn hydrogenolysis in the presence of a suitable catalyst such as palladium on carbon also affords the corresponding carboxylic acid 11.
As shown in Scheme 4 below, the synthetic procedures leading to isoxazoline- and isoxazolinone-substituted quinolones of the present invention closely parallel the above procedure. 
In another embodiment, the linking group between the oxazolidinone, isoxazoline, or isoxazolinone ring and the quinolone ring of the quinolone compounds (Scheme 1) of the present invention is a bond. In these cases, the oxazolidinone, isoxazoline, and isoxazolinone is formed subsequent to the nucleophilic substitution reaction. This is illustrated in Scheme 5. 
For example, quinolone (1) is treated with 1-acetyl-3-amino-2-(S)-oxypropylamine in NMP and NMM, as described above, to form an aminoalcohol intermediate (18). The aminoalcohol intermediate (18) then is converted, in a one-pot reaction sequence, to a crude oxazolidinone-substituted quinolone (19) by treatment with carbonyldiimidazole (CDI). Conversion of amino alcohols to oxazolidinones is achieved by known process as (See e.g., J. Med. Chem., 32, 1673 (1989).).
In another embodiment, the oxazolidinone-, isoxazoline-, and isoxazolinone-substituent is covalently bonded to the one-position nitrogen of the quinolone ring system. Scheme 6 illustrates the synthesis of a 1-oxazolidinone-substituted quinolone compound of the present invention. 
Briefly, ethyl 3-dimethylaminoacrylate (20) is converted to ethyl 2-(dimethylamino)methylene-2-(2,4,5-trifluorobenzoyl)acetate (21) in the presence of 2,4,5-trifluorobenzoyl chloride, triethylamine, and 1,4-dioxane. Reaction of compound (21) with 5-(S)-acetamidomethyl-3-(4-amino-3-fluorophenyl)-oxazolidine-2-one provides compound (22), which then is heated in the presence of diazabicyclo[4.4.0]undec-2-ene (DBU) and an excess of NMP to facilitate cyclization to quinolone-oxazolidinone (23). Quinolone-oxazolidinone (23) can be converted directly to the corresponding N-methylpiperazinyl compound (24) by treatment with 1-methylpiperazine in the presence of NMP. Hydrolysis of compound (24) in the presence of aqueous hydrogen chloride yields acid amine (25). Acylation of amine (25) provides a oxazolidinone-substituted quinolone (26) of the present invention. The synthetic procedures which provide the N1-isoxazoline- and isoxazolinone-substituted quinolones of the present invention closely parallel the above procedure.
Isoxazoline- and isoxazolinone intermediates (12), (14), and (15) can be obtained a variety of syntheses. The preferred routes are depicted in Schemes 7 and 8, respectively. It will be apparent to those skilled in the art that the following are representative examples, and that modifications of the disclosed synthetic protocols allow for the preparation of isoxazoline- and isoxazolinone intermediates. 
As shown in Scheme 7, p-fluorobenzaldehyde (27) can be reacted with commercially available BOC-protected piperazine, 1-(t-butoxycarbonyl)piperazine (Aldrich Chemical Company, Inc., Milwaukee, Wis.), in the presence of potassium carbonate and a suitable solvent, such as pyridine (Py), and at a suitable temperature (e.g., reflux) to provide piperazinyl intermediate (28). The formation of ester alcohol (29) results from the condensation of Compound (28) with ethyl diazoacetate, as described in Mahmood et al., J. Org. Chem., 63, pgs. 3333-3336 (1998). Addition of hydroxylamine, followed by warming to reflux in aqueous methanol, yields piperazinylarylisoxazolinone (30). Compound (30) then is converted to the corresponding methylacetamide (31) by reaction with N-(hydroxymethyl)acetamide acetate/DMF. The BOC group then is removed by treatment with an acid, preferably trifluoroacetic acid in dichloromethane (DCM), to yield piperazinylarylisoxazolinone Compound (12).
As shown in Scheme 8, intermediate (28) also can be reacted with hydroxylamine hydrochloride in a polar protic solvent, such as methanol (MeOH), in the presence of a base, such as pyridine, to afford oxime (32). The oxime (32) then is oxidized by N-chlorosuccinamide (NCS) in an appropriate solvent, such as dichloromethane, to give the oximyl chloride (33) Alternatively, oximyl chloride (33) can be formed in situ and directly treated with an allylic compound such as N-acetylallylamine or allyl alcohol, in the presence of a suitable solvent, such as dichloromethane (DCM), to give compounds (34) and (35), respectively. The BOC protecting group then is removed by reaction with an acid, preferably trifluoroacetic acid in dichloromethane, to furnish piperazinylarylisoxazolinone compounds (14) and (15), respectively. 
Other combinations of a quinolone with an oxazolidinone, an isoxazolinone, or an isoxazoline, also are possible. One embodiment involves covalent binding of the oxazolidinone, isoxazolinone, or isoxazoline to the side chains of the preferred C-7 quinolone substituents, for example the side chain amino group of optically active (amino)cycloalkylamino C-7 substituents.
The oxazolidinone- and isoxazoline-substituted quinolones (I) of the present invention contain at least one chiral center. It is apparent to one skilled in the art that when one chiral center is present, the compound can exist as one of two possible optical isomers ((R) and (S) enatiomers) or a racemic mixture of both. Both individual (R) and (S) enatiomers, as well as mixtures thereof, are within the scope of the oxazolidinone- and isoxazoline-substituted quinolones (I) of the invention. In the event a second chiral center is present in the oxazolidinone- and isoxazoline-substituted quinolones (I) of the invention, the resultant diastereomers, in racemic and enantiomerically enriched forms, also are within the scope of the compounds (I) of the invention.
The preferred compounds of the present invention are optically pure enantiomers having the (S)-configuration at C5 of the oxazolidinone or isoxazoline ring, because, for example, S-ofloxacin exhibits a 10 to 100-fold greater potency than R-ofloxacin. However, the racemic mixture also is useful, but a greater amount of the racemic material may be required to produce the same effect as the pure S-enantiomer.
If desired, the mixture of enantiomers is resolved by means known to those skilled in the art. Optically pure material can be obtained by resolution of the racemic mixture by HPLC using a chiral phase, such as a Chiralpack AD column as described in Examples 4 and 6 for compounds 15 and 17 and shown in Scheme 2. Alternatively, resolution of the racemic mixture can be accomplished by selective crystallization of a salt form using methods known to those skilled in the art. See for example, xe2x80x9cOptical Remixture Procedures for Chemical Compounds, Vol 1; Amines and Related Compounds,xe2x80x9d Paul Newman, Optical Remixture Information Center, Manhattan College, Riverdale, N.Y., 10471, 1978. For example, treatment of the R,S-aminomethyl mixture (25) with an appropriate optically active acid, such as (+)-tartaric acid, or alternatively with (xe2x88x92)-tartaric acid, yields a mixture of diastereomeric salts, which can be separated by fractional crystallization to give a salt containing one enantiomer of the racemic mixture. Other suitable optically active acids include (xe2x88x92)-dibenzoyl-tartaric acid, (+)-camphoric acid, (+)- and (xe2x88x92)-malic acid, and (+)-camphor-10-sulfonic acid. By reacting the diastereomeric salt with a base, the optically pure free amino compound (25) is obtained
A compound of formula (I), or a prodrug or a physiologically acceptable salt or solvate thereof, can be administered as the neat compound or as a pharmaceutical composition containing either entity.
The pharmaceutical compositions of the present invention can be prepared by admixing a compound of formula (I) with a solid or liquid pharmaceutically acceptable carrier, and, optionally, with pharmaceutically acceptable adjuvants and excipients employing standard and conventional techniques. Solid form compositions include powders, tablets, dispersible granules, capsules, cachets and suppositories. A solid carrier can be at least one substance which also can function as a diluent, flavoring agent, solubilizer, lubricant, suspending agent, binder, tablet disintegrating agent, and encapsulating agent. Inert solid carriers include magnesium carbonate, magnesium stearate, talc, sugar, lactose, pectin, dextrin, starch, gelatin, cellulosic materials, a low melting wax, cocoa butter, and the like. Liquid form compositions include solutions, suspensions, and emulsions. For example, compounds of the present invention can be dissolved in water, water-propylene glycol, or water-polyethylene glycol, optionally containing suitable conventional coloring agents, flavoring agents, stabilizers and thickening agents. The oxazolidinone-, isoxazoline-, and isoxazolinone-substituted quinolones (I) can be used alone, or in conjunction with other antibacterial agents and/or non-antibacterial agents, as known to those skilled in the art.
Pharmaceutically acceptable refers to those properties and/or substances which are acceptable from a pharmacological or toxicological point of view and from a physical or chemical point of view regarding composition, formulation, stability, patient acceptance, and bioavailability. Pharmaceutically acceptable hydrate means hydrates useful for administering the compounds of this invention, and suitable hydrates include the compounds complexed with at least one water molecule.
Pharmaceutically acceptable salts means salts useful for administering compounds of the present invention. Suitable salts include acid addition salts when a basic group is present, such as occurs with the preferred piperazinyl group. Acid addition salts include those made from mineral adds, for example, hydrochloric, hydrobromic, hydroiodic, sulfuric, phosphoric, and the like, organic sulfonic acids, e.g., methanesulfonic, 2-hydroxyethyl sulfonates, organic carboxylic acids, e.g., amino and carbohydrate acids, e.g., gluconic, galacturonic, acetates, propionates, lactates, maleates, malates, succinates, tartrates, citric acid, fumarates, and the like. These salts can be in a hydrated form.
Pharmaceutically acceptable prodrugs means prodrugs useful for administering the compounds of this invention. Suitable prodrugs include acid derivatives, for example, amides, esters, for example, methyl esters, ethyl esters, and the like. It also is appreciated by those skilled in the art that the appropriate N-oxides of the nitrogens of the oxazolidinone-, isoxazoline-, and isoxazolinone-substituted quinolones (I) are included within the scope of the invention. These prodrugs also can be in a hydrated form.
Compounds and pharmaceutical compositions suitable for use in the present invention include those wherein the active ingredient is administered in an effective amount to achieve its intended purpose. More specifically, a xe2x80x9ctherapeutically effective amountxe2x80x9d means an amount effective to prevent development of, or to alleviate the existing symptoms of, the subject being treated. Determination of the effective amounts is well within the capability of those skilled in the art, especially in light of the detailed disclosure provided herein.
A xe2x80x9ctherapeutically effective dosexe2x80x9d refers to that amount of the compound that results in achieving the desired effect. Toxicity and therapeutic efficacy of such compounds can be determined by standard pharmaceutical procedures in cell cultures or experimental animals, e.g., for determining the LD50 (the does lethal to 50% of the population) and the ED50 (the dose lethal to 50% of the population). The dose ratio between toxic and therapeutic effects is the therapeutic index, which is expressed as the ratio between LD50 and ED50. Compounds which exhibit high therapeutic indices are preferred. The data obtained from such data can be used in formulating a dosage range for use in humans. The dosage of such compounds preferably lies within a range of circulating concentrations that include the ED50 with little or no toxicity. The dosage can vary within this range depending upon the dosage form employed, and the route of administration utilized.
Humans and other mammals, for example, cattle, horses, sheep, hogs, dogs, and cats, can be treated with the oxazolidinone-, isoxazoline-, and isoxazolinone-substituted quinolones (I) of the present invention. The quinolones (I) of the present invention can be administered in a manner and in dosage forms similar to those of the known anti-bacterial agents described above. In therapeutic use for treating, or combating, bacterial infections in humans and warm-blooded animals, the compounds of formula (I), or pharmaceutical compositions thereof, are administered by conventional techniques, such as orally in solid and liquid dosage forms and/or parenterally (IV, IM, SQ), at a unit dosage form to obtain and maintain a concentration, that is, an amount, or blood-level of active component in the animal undergoing treatment which is antibacterially effective or appropriate.
Generally, the amount of compound (I) in a pharmaceutical composition is about 0.5% to about 90% by weight. An antibacterially effective dosage of compound (I) is about 0.1 to about 100 mg/kg of body weight/day, more preferably about 3 to about 50 mg/kg of body weight/day. The quantity of the oxazolidinone-, isoxazoline-, and isoxazolinone-substituted quinolone compounds of formula (I) in the pharmaceutical composition, the exact unit dosage form thereof to be administered, the frequency of administration, and the route of administration will vary, and can be adjusted widely depending upon a number of factors known to those skilled in the art including the particular mode of administration, the particular compound being used, the potency of the particular compound, the desired concentration, the age, weight, sex, and general physical condition and requirements of the patient, the nature and severity of the bacterial infection being treated, and the like, as is well known to the physician treating infectious diseases. Also, it is to be understood that the initial dosage administered can be increased beyond the above upper level in order to rapidly achieve the desired blood-level or the initial dosage can be smaller than the optimum and the daily dosage can be progressively increased during the course of treatment depending on the particular situation. The usual pharmaceutical dosage forms appropriate for parenteral (mixture, suspension in oil) and oral (tablet, capsule, syrup, suspension, etc) administration are known to those skilled in the art.
Compounds of the present invention can be administered by any suitable route, for example by oral, topical, buccal, inhalation, sublingual, rectal, vaginal, transurethral, nasal, topical, percutaneous, i.e., transdermal, or parenteral (including intravenous, intramuscular, subcutaneous, and intracoronary) administration. Parenteral administration can be accomplished using a needle and syringe, or using a high pressure technique, like POWDERJECT(trademark).
If the compounds or pharmaceutical compositions of the present invention are administered parenterally, i.e., by injection, for example, by intravenous injection or by other parenteral routes of administration, it generally is as a soluble salt (acid addition salt or base salt) of the compound according to formula (I) in a pharmaceutically acceptable amount dissolved in a pharmaceutically acceptable liquid carrier such as, for example, water-for-injection, and a buffer to provide a suitable buffered isotonic solution, for example, having a pH of about 3.5 to about 6.
Suitable buffering agents include, for example, trisodium orthophosphate, sodium bicarbonate, sodium citrate, N-methylglucamine, L(+)-lysine, and L(+)-arginine. A compound of formula (I) generally is dissolved in the carrier in an amount sufficient to provide a pharmaceutically acceptable injectable concentration in the range of about 1 to about 400 mg/ml of solution. The resulting liquid pharmaceutical composition is administered so as to obtain the above-mentioned antibacterially effective amount of dosage.
For human use, a compound of the formula (I) can be administered alone, but generally is administered in admixture with a pharmaceutical carrier selected with regard to the intended route of administration and standard pharmaceutical practice. Pharmaceutical compositions for use in accordance with the present invention can be formulated in a conventional manner using one or more physiologically acceptable carriers comprising excipients and auxiliaries that facilitate processing of compounds of formula (I) into preparations which can be used pharmaceutically.
These pharmaceutical compositions can be manufactured in a conventional manner, e.g., by conventional mixing, dissolving, granulating, dragee-making, levigating, emulsifying, encapsulating, entrapping, or lyophilizing processes. Proper formulation is dependent upon the route of administration chosen. When a therapeutically effective amount of a compound of the present invention is administered orally, the composition typically is in the form of a tablet, capsule, powder, solution, or elixir. When administered in tablet form, the composition can additionally contain a solid carrier, such as a gelatin or an adjuvant. The tablet, capsule, and powder contain about 5 to about 95% compound of the present invention, and preferably from about 25 to about 90% compound of the present invention. When administered in liquid form, a liquid carrier such as water, petroleum, or oils of animal or plant origin can be added. The liquid form of the composition can further contain physiological saline solution, dextrose or other saccharide solutions, or glycols. When administered in liquid form, the composition contains about 0.5 to about 90% by weight of a compound of the present invention, and preferably about 1 to about 50% of a compound of the present invention.
When a therapeutically effective amount of a compound of the present invention is administered by intravenous, cutaneous, or subcutaneous injection, the composition is in the form of a pyrogen-free, parenterally acceptable aqueous solution. The preparation of such parenterally acceptable solutions, having due regard to pH, isotonicity, stability, and the like, is within the skill in the art. A preferred composition for intravenous, cutaneous, or subcutaneous injection typically contains, in addition to a compound of the present invention, and isotonic vehicle.
For oral administration, the compounds can be formulated readily by combining a compound of formula (I) with pharmaceutically acceptable carriers well known in the art. Such carriers enable the present compounds to be formulated as tablets, pills, dragees, capsules, liquids, gels, syrups, slurries, suspensions and the like, for oral ingestion by a patient to be treated. Pharmaceutical preparations for oral use can be obtained by adding a compound of formula (I) with a solid excipient, optionally grinding a resulting mixture, and processing the mixture of granules, after adding suitable auxiliaries, if desired, to obtain tablets or dragee cores. Suitable excipients include, for example, fillers and cellulose preparations. If desired, disintegrating agents can be added.
For administration by inhalation, compounds of the present invention can be delivered in the form of an aerosol spray presentation from pressurized packs or a nebulizer, with the use of a suitable propellant. In the case of a pressurized, aerosol, the dosage unit can be determined by providing a valve to deliver a metered amount. Capsules and cartridges of, e.g., gelatin, for use in an inhaler or insufflator can be formulated containing a powder mix of the compound and a suitable powder base such as lactose or starch.
The compounds can be formulated for parenteral administration by injection, e.g., by bolus injection or continuous infusion. Formulations for injection can be presented in unit dosage form, e.g., in ampules or in multidose containers, with an added preservative. The compositions can take such forms as suspensions, solutions, or emulsions in oily or aqueous vehicles, and can contain formulatory agents such as suspending, stabilizing, and/or dispersing agents.
Pharmaceutical formulations for parenteral administration include aqueous solutions of the active compounds in water-soluble form. Additionally, suspensions of the active compounds can be prepared as appropriate oily injection suspensions. Suitable lipophilic solvents or vehicles include fatty oils or synthetic fatty acid esters. Aqueous injection suspensions can contain substances which increase the viscosity of the suspension. Optionally, the suspension also can contain suitable stabilizers or agents that increase the solubility of the compounds and allow for the preparation of highly concentrated solutions. Alternatively, a present composition can be in powder form for constitution with a suitable vehicle, e.g., sterile pyrogen-free water, before use.
Compounds of the present invention also can be formulated in rectal compositions, such as suppositories or retention enemas, e.g., containing conventional suppository bases. In addition to the formulations described previously, the compounds also can be formulated as a depot preparation. Such long-acting formulations can be administered by implantation (for example, subcutaneously or intramuscularly) or by intramuscular injection. Thus, for example, the compounds can be formulated with suitable polymeric or hydrophobic materials (for example, as an emulsion in an acceptable oil) or ion exchange resins, or as sparingly soluble derivatives, for example, as a sparingly soluble salt.
For topical administration, the present compounds can be applied in neat form, e.g., when the compound is a liquid. However, it is desirable to administer the compounds to the skin as compositions in combination with a dermatologically acceptable carrier, which can be a solid, semi-solid, or a liquid. Useful solid carriers include, but are not limited to, finely divided solids such as talc, clay, microcrystalline cellulose, silica, alumina, and the like. Useful liquid carriers include, but are not limited to, water, alcohols, glycols, and water-alcohol/glycol blends in which the present compounds can be dissolved or dispersed at effective levels, optionally with the aid of a surfactant. Adjuvants, such as fragrances and additional antimicrobial agents, can be added to optimize the properties for a given use. The resultant liquid compositions can be applied topically by absorbent pads, used to impregnate bandages and other dressings, or sprayed onto the affected area using pump-type or aerosol sprayers.
For veterinary use, a compound of formula (I) or a nontoxic sale thereof, is administered as a suitably acceptable formulation in accordance with normal veterinary practice. The veterinarian can readily determine the dosing regimen and route of administration that is most appropriate for a particular animal.
Reagents were purchased from commercial sources and used without further purification. All temperatures are in degrees Centigrade. When solvent pairs are used, the ratios of solvents used are volume/volume (v/v). When the solubility of a solid in a solvent is used the ratio of the solid to the solvent is weight/volume (wt/v). Reactions with moisture-sensitive reagents were performed under a nitrogen atmosphere. Concentration of solutions was performed by reduced pressure rotary evaporation. Brine refers to an aqueous saturated sodium chloride mixture. High performance liquid chromatography (HPLC) analysis and purification were performed using Beckman System Gold(copyright); detection at 220 nm. Analytical HPLC was performed on a YMC 5 micron C18 (4.6 mmxc3x9750 mm) reverse phase (RP) column (gradient from 100% of the aq. 0.1% trifluoroacetic acid (TFA) to 100% of 0.1% TFA in acetonitrile (MeCN) over 6 min, flow rate 2.0 mL/min). Preparative thin-layer chromatography (TLC) were performed using EM silica gel (SG) 60 F254 plates (20xc3x9720 cm, thickness 2 mm). NMR refers to nuclear magnetic resonance spectroscopy. 1H NMR refers to proton nuclear magnetic resonance spectroscopy with chemical shifts reported in ppm downfield from tetramethylsilane. Mass-spectra (MS) refers to mass spectrometry expressed as m/e or mass/charge unit and was obtained using electron impact (EI) technique. [M+H]+ refers to the positive ion of a parent plus a hydrogen atom. Retention time (Rt) is in minutes and refers to x. IR refers to infrared spectroscopy. FTIR refers to Fourier Transform IR.
In the following examples, the following abbreviations are used: millimole (mmol), milliliter (mL), potassium carbonate (K2CO3), ethyl acetate (EtOAc), DMSO (dimethyl sulfoxide), magnesium sulfate (MgSO4), sodium bicarbonate (NaHCO3), and ethyl alcohol (EtOH).